Beneficiation of sylvinite ore

ABSTRACT

Coarse clay-containing sylvinite having a maximum particle size of from about 3/4 inch to about 3/8 inch is divided into two portions by sizing at about 1/4 inch to about 4 mesh and the coarser fraction containing unliberated ore particles is subjected to gravity separation to reject significant amounts of clay and halite. Both the concentrate from the gravity separation which is comminuted to liberate mineral constituents and the minus 1/4 inch to 4 mesh fraction from the initial sizing are subjected to gravity beneficiation.

I United States Patent 11 1 1111 3,802,632 Dancy Apr. 9, 1974 [54] BENEFICIATION OF SYLVINITE ORE 3,167,502 1/1965 Duke 209/12 1 3,417,927 121909 C k 24] 24 [75] Inventor: William B. Dancy, Carlsbad, N. 3,677475 ai iff I I 4 X 3,746,265 7/1973 Dancy 209/17 x Assigneez International Minerals & Chemical 3,750,963 8/1973 Dancy 24l/2O Corporation, y ll FOREIGN PATENTS OR APPLICATIONS 22 i O 24 1972 792,819 8/l968 Canada 209/172.5

[2].] Appl' 300l31 Primary Examiner-Robert Halper Related US. Application Data Attorney, Agent, or Firm.lames E. Wolber; Peter [63] Continuation-impart of Ser. No. 77,632, Oct. 2, Andress 1970, abandoned.

[57] ABSTRACT [52] US. Cl 241/20, 209/3, 209/172.5, C l l h 209 M11, 2O9/166 oarse c ay-corf1ta1nmg sy v1n1 te avmg a ma umurn 51 lnt.Cl B03b 3/44, B03b 9/00 gi l g f f 2 s: 39 58 Field Of Search ..209/2,3,172,l72.5,166, e W0 i a 209 /211 17, 241/20 2 4 about 4 mesh and the coarser fraction containing unllberated ore part1cles 1s sub ected to gravity separa- [56] References Cited tion to reject significant amounts of clay and halite. Both the concentrate from the gravity separation I UNITED STATES PATENTS which iscomminuted to liberate mineral constituents 2,913,502 4/1960 SChOCld 209/164 and the minus 14 inch to 4 fraction from the ini- 21932-395 4/ 1960 1 209/172-5 tial sizing are subjected to gravity beneficiation. 3,008,655 11/1961 Adams 209/12 X 1 3,037,624 6/1962 Jackson 209/12 X 24 Claims, 1 Drawing Figure ORE 1 CRUSHER a" 1 ii 4 4 XIOM CRUSHER CONCENTRATE j j :11 HYDROCYCLONE CONCENTRATE 5 HYDROCYCLONEI' TAl LS DESLIME PAIENTED PR 9 m4 1802.632

ORE

{I CRUSHER L IOM ll ll x 4 4 ll 4 XIOM 1 w v H 5 HYDROCYCLONE HYDROCYCLONE 13 FAQ TAILS /7 TAILS HYDROCYCLONE 15 s CRUSHER 16 u N18 14m 9 CRUSHER CONCENTRATE L 19 DESLIME CONCENTRATE 4 J 21 FLOTATION l AILS lmgg BENEFICIATION OF SYLVINITE ORE CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 77,632 now abandoned, filed Oct. 2, 1970 and entitled Beneficiation of Sylvinite Ores. The benefit of the filing date of said earlier application is claimed as to the common subject matter.

DESCRIPTION OF THE INVENTION This invention relates to the beneficiation of sylvinite ores and, more particularly, to the beneficiation of clay-containing sylvinite ores.

Sylvinite ore such as that found in the Delaware arm of the Permian basin in the United States may contain from about 3 percent to about 7 percent or more of clay. Similar high-clay ores are also found in France and Germany. In addition, sylvinite ore, such as that found in the Saskatoon region of Saskatchewan, may contain from about 5 percent to about 6 percent or more of clay.

Unfortunately, the degree of comminution required for liberation of ore values in a high-clay ore provides a disproportionate amount of fine colloid clay particles commonly referred to as slimes which tend to clog the processing circuits and absorb processing chemicals. Efforts to deslime high-clay ores, such as by use of settling tanks, hydro-separators, and the like, have not proven entirely satisfactory. As a consequence, the processing of clay-containing sylvinite such as that found in the Saskatoon region does not compare favorably economically with processing of low-clay sylvinite.

It is one object of this invention to provide a process for the beneficiation of high-clay sylvinite ores.

It is a further object of this invention to provide a process wherein a substantial portion of the clay is removed with coarse halite.

It is another object of this invention to provide a process wherein a substantial portion of the clay is removed before the sylvinite is finely comminuted.

The present invention contemplates a process for beneficiating a clay-containing sylvinite ore containing at least about 3 percent clay and having a K O:clay ratio of less than about 5:1 comprising:

1. comminuting said sylvinite ore to provide particles having a maximum size of from about inch to about l inch;

2. sizing said comminuted ore to provide a first fraction containing particles having sizes greater than about /1 inch and a second fraction having sizes ranging from about inch to about mesh;

3. subjecting said first fraction to gravity separation in a media having a specific gravity of separation intermediate the specific gravity of sylvite and halite whereby sylvite-containing particles are removed as an overflow fraction characterized by a K ozclay ratio of at least about 8:1 and halite and clay particles are removed as an underflow;

4. comminuting said overflow fraction from (3) to provide a fraction having particles ranging from about 4 inch to about 10 mesh; and

5. subjecting said fraction from (3) and said second fraction from (2) to gravity separation in a media having a specific gravity of separation intermediate the specific gravity of sylvite and halite whereby sylvitecontaining particles are removed! as an overflow concentrate.

In some instances, depending upon the liberation characteristics of the ore, it will be more advantageous with respect to sylvinite recovery to carry out the process substantially as hereinbefore described, with the modification that initial comminution of step (I) will provide particles having a maximum size of from about inch to about inch; the sizing of step (2) will provide a first fraction containing particles having sizes greater than about 4 mesh and a second fraction having a size range from about 4 mesh to about 10 mesh; and the comminuting of step (4) will provide a fraction having particles ranging from about 4 mesh to about 10 mesh. This variation of the process will be most advantageously employed with relatively more finelyliberating ore and will result in the avoidance of excessive loss of sylvite values to the first gravity separation underflow. Ores susceptible to treatment in this way are those in which the +4 mesh particles will be mostly or entirely unliberated with respect to sylvite. For those ores where particles larger than 4 mesh, say, 4 inch or inch, are mainly liberated with respect to sylvite, this alternate embodiment is not recommended and it is preferred that the initial comminution be one which provides particles having amaximum size of from $4 inch to about /2 inch, as before described.

In one preferred embodiment of the invention the overflow concentrate from (5) is subjected to a second gravity separation in a media having a specific gravity of separation intermediate the specific gravity of sylvite and halite whereby a sylvite product is obtained as an overflow. The underflow may be subjected to wet beneficiation. In another preferred embodiment of the invention the -l0 mesh particles resulting from comminution, such as the comminution of steps (1) and (4) above, are subjected to wet beneficiation, i.e., froth flotation or crystallization.

Since clays or insoluble slime-forming minerals tend to be softer than sylvite or halite, a disproportionate amount of colloid particles are formed when a highclay sylvinite ore is comminuted to liberation. This invention minimizes the difficulty presented by slimes by providing a process wherein coarse ore is subjected to gravity separation which removes halite and a significant amount of the clay present. In this regard, it has been noted that the clay is predominately associated with the halite and that an initial gravity separation is a feasible way to remove both coarse halite and clay. The coarse ore can be screened to provide a plug Aiplus inch fraction (with some ores better a plus 4 mesh fraction) that may be subjected to gravity separation to reject significant quantities of undesirable halite and clay without the loss of substantial amounts of K 0 values. The gravity separation is effective even though the ore has not been ground to liberation.

The beneficiation of sylvinite by gravity separation is described generally in Canadian Pat. No. 792,819. The particular process of this invention is especially designed for the beneficiation of clay-containing sylvinite found in the Saskatoon region of Saskatchewan or in the Delaware arm of the Permian basin. Ore in the Sas-, katoon region of Saskatchewan generally will contain at least about 5 percent clay and generally will contain from about 5 percent to about 6 percent or more of clay. The K Ozclay ratio of the ore is less than about 5.5:1. Frequently, the ore will contain from about 25 percent to about 30 percent sylvite as K 0. Sylvinite found in the Delaware arm of the Permian basin (and comparable sylvinite found in France and Germany) generally will contain at least about 3 percent clay and generally from about 3 percent to about 7 percent or more of clay. Such ores have a K ozclay ratio of only about :1 or less. Frequently, the ore will contain from about 12 percent to about 22 percent sylvite as K 0. A

typical ore may contain about 4 percent clay and about 17 percent sylvite as K 0.

The ores to which the present invention is directed will also contain halite and may contain minor amounts of constituents such as polyhalite, kainite, kieserite, magnesium sulfate and/or leonite. Comminution to about A inch provides liberation of the sylvite constituent of Saskatoon ore and of sections of other claycontaining sylvinite ore such as that found in the Delaware arm of the Permian basin and the like. Other sections of Permian basin ore require comminution to about 4 mesh. The term liberation is employed herein to designate that degree of comminution which permits the ore to be physically separated into a sylvite concentrate having an analysis of 55 percent K 0 or more and containing at least about 80 percent of the sylvite K 0 values originally present in the ore. It will be appreciated that liberation of the sylvite constituent of specific ore deposits within the region may vary somewhat from A inch.

The term clay as employed herein embraces not only true clay minerals such as montmorillonite, kaolin, and attapulgite but also other slime-forming waterinsolubles such as dolomite, silica, and the like. These materials all form troublesome colloids or semi-colloids and, therefore, behave much like true clays in the processing circuit. All of the materials termed clays are water-insoluble minerals that tend to form slimes.

This invention permits at least about 30 percent of the clay present in'the initial ore to be removed in the initial gravity separation of coarse material. Generally, at least about percent of the halite present in the initial ore will also be removed. The amount of clay and halite removed will depend upon particular ore being processed and the operating conditions chosen. In the preliminary separation, less than about 5 percent sylvite need be lost.

Generally, process conditions such as degree of comminution, gravity for separation, and the like, will be chosen so that the total K Ozclay ratio of the overflow from the initial gravity separation will be at least about 8:1. The process is also desirably operated to provide 1 0 mesh material which is characterized by an overall K ozclay weight ratio of at least about 8:1, and preferably about lOzl.

It is preferred that the ore initially be crushed to about inch since about 54 inch particles are the largest that feasibly can be beneficiated in a gravity separator for the purposes of this invention. Comminuting only to inch mesh avoids, to the maximum extent, unnecessary breaking up of the clay. While ores comminuted to -34 inch (particles ranging in size from about inch) are preferred for the practice of this in-' vention, advantageous results can also be obtained employing ores comminuted to about inch, or to a maximum size intermediate of inch and /2 inch. Comminution to provide a maximum particle size of k inch to inch is recommended only where necessary to avoid excessive sylvite losses to the underflow of the first gravity separation. It will be appreciated that as the maximum size of comminution is decreased, increasingly more clay tends to be converted to slimes and that the maximum acceptable comminution will vary somewhat depending upon the precise ore being processed.

For ease of presentation, the practice of the invention will be described hereinafter with reference to the processing of a inch X +10 mesh ore fraction and to separation at A inch. The mesh sizes referred to herein are standard Tyler mesh sizes.

The process of this invention readily can be carried out employing standard equipment well-known in the art. For example, either wet or dry comminution may be employed in the practice of this invention, and suitable apparatus includes a ball mill, hammer mill, rod mill, impact crusher, or the like. Such equipment will provide particles ranging from a selected maximum size downward. Since it is desirable to maintain as much clay as possible in the larger fraction, comminution is preferably maintained at a minimum, consonant with the size requirement for the ore.

In a preferred embodiment wherein froth flotation is employed and ore particles have sizes ranging from 541 inch to 10 mesh, it is desirable that at least 30 percent of the particles have a size of about inch or larger.

In one embodiment, this invention contemplates drying mine run ore or coarse crushed ore to remove free Water from the clay and thereby provide a clay somewhat less susceptible to slime formation. Drying generally may be accomplished at temperatures between about F. and about 700F. Time of drying will obviously vary depending upon the temperature. In a typical drying step, ore may be maintained at about 350F. for about 10 to 20 minutes.

Comminution will, of course, provide some fines which may interfere with the gravity separation by altering the specific gravity of the medium or by interfering with the separation of weighting agent from the ore particles. Accordingly, the comminuted ore is sized employing hydrocones, rake classifiers, screens, or the like to remove at least the l0 mesh fraction. The 10 mesh fraction may be deslimed and beneficiated by conventional flotation or crystallization techniques as will be discussed more fully below.

The comminuted fraction is screened at about Vi inch to provide one fraction having particles with sizes greater than about 4 inch and a second fraction having particles with sizes less than about A inch. In effect, the first fraction contains unliberated ore while the mineral constituents of the second fraction have been liberated. Even though the larger fraction contains unliberated ore, it has been determined that this fraction may be subjected to gravity separation to reject substantial amounts of clay and halite without the concurrent loss of an unacceptable amount of K 0 values.

Each fraction from the sizing step is subjected to gravity separation employing a liquid that has a gravity intermediate the gravity of halite (approximately 2.17 at 20C.) and sylvite (approximately 1.99 at 20C.). Typical vessels employed for gravity separation include cones, classifiers, drum-type vessels or vortex separatory vessels such as hydrocyclones. In order to minimize generation of clay particles during handling of the ore, it is advisable to avoid abrasive conditions during the pulping of the ore in the heavy media.

The liquid media employed for the gravity separation may be either a so-called heavy media" or a so-called heavy liquid. A heavy media is a suspension of a weighting agent, or a mixture of weighting agents, in a brine which is preferably substantially saturated with respect to the sylvinite feed. Ferrous media, such as magnetite and/or ferrosilicon, are preferred weighting agents because of their commercial availability, low cost, ease of recovery and cleaning by magnetic means, and ability to form a fluid medium of the predetermined specific gravity in the brine. The ferrous media are usually used as substantially all minus 100 mesh particles. These are very readily suspended in the brine and the resultant suspension is self-sustaining with the moderate agitation produced by recycling the suspension in thenormal operation. Halogenated hydrocarbons and mixtures thereof are suitable for use as heavy liquids Illustrative of such halogenated hydrocarbons are methylene bromite (specific gravity of 2.49) and methylene chlorobromide (specific gravity of 1.92). Fluorine substituted and iodine substituted alkyl compounds may also be used.

The terms circulating gravity and specific gravity of separation will be used herein in accordance with the general usage in the art. Thus, circulating gravity means and refers to the actual density of the separating medium, while specific gravity of separation" means and refers to the apparentv density of the separating medium based on the separations which can be made with it in a specific separating vessel. When the separatory vessel used is one in which the-path taken by'the individual particles is determined only by their respective specific gravities, such as a conventional cone, classifier or drum-type vessel, the circulating gravity and specific gravity of separation will be the same. In suchinstances, the separating medium (either circulating or in the separation vessel) will have a specific gravity intermediate the specific gravities of the sylvite and halite. However, when a vortex separatory vessel is employed as in the preferred embodiment of this invention, use is made of centrifugal forces which are many times greater than gravity. In such instances, a given heavy media may itself have a specific gravity, i.e., a circulating gravity, of less than the gravity of either halite or sylvite but may produce a separation in a vortex vessel such as ,a hydrocyclone between the sylvite and the halite because the forces in the vessel provide a heavier specific gravity of separation. For example, a circulating gravity of 1.85 may provide a media in the vortex vessel that has the characteristics of a 2.1 specific gravity. The specific gravity of separation of such a heavy media would then be said to be about 2.1. The relationship between circulating gravity and specific gravity of separation will vary somewhat depending upon the apparatus and operating conditions. but is readily within the skill of the routineer.

Gravity separation of the inch fraction provides an overflow containing a major portion of the sylvite content of the fraction which is substantially diminished in clay content. This overflow, after removal of the heavy media, if desired, is comminuted to liberate the mineral constituents (i.e., inch) and thereafter may be beneficiated by gravity separation with the inch fraction from the initial sizing step to provide an overflow sylvite concentrate. The inch material desirably is subjected to both a rougher and to a cleaner separation. The liquid media specific gravity of separation for the rougher separation generally will be between about 2.10 and 2.16 while the specific gravity of separation for the cleaner separation will be between about 2.02 and about 2.06. When employing both a rougher and cleaner separation, the overflow sylvite-containing fraction from the rougheris sent to the cleaner and the overflow from the cleaner constitutes the sylvite concentrate. Halite and clay are rejected as underflow from the rougher while the underflow from the cleaner may be comminuted and recycled to the rougher or subjected to wet beneficiation.

It is likely that sufficient 10 mesh material will be generated in the process to justify beneficiation of this material also. This material can be beneficiated readily by either conventional froth flotation or by conventional crystallization. The term wet beneficiation is employed herein to denote either froth flotation or crystallization.

In a conventional wet beneficiation of 1 O mesh particles, slimes can be removed in a hydroseparator and the deslimed ore beneficiated. In froth flotation, the

ore may be reagentized with a cationic flotation agent; and the fraction subjected to froth flotation. Suitable cationic flotation agents include aliphatic amines, such as n-lauryl amine; and high molecular weight aliphatic amines containing about 14 to 20 carbon atoms and their water-soluble addition salts, as well as quaternary ammonium salts, as for example, octadecylamine acetate, hexadecylamine hydrochloride, and the like. The conditioned ore is finally fed into a suitable flotation vessel, which usually consists of a battery of units in parallel or in series. The flotation is effective to remove as an overflow concentrate a substantial amount of the sylvite content of the fine fraction together with some of the halite. The flotation concentrate is dried and sent to storage. The underflow tail from the flotation operation, predominating in halite and containing a minor amount of sylvite, is removed and discarded as waste.

In a conventional crystallization process, ore is contacted with heated brine unsaturated with respect to KCl but saturated with respect to'NaCl in order to solubilize KCI in the ore. Thereafter, the brine is cooled to deposit KCl crystals. Since the solubility of NaCl is not affected by temperature changes in the same manner as KC], the process is selective for the production of KCl crystals.

The accompanying drawing is a diagrammatic flow sheet illustrating a preferred embodiment of the process of this invention.

Ore is fed to crusher 1 to provide inch particles. These particles are sized in screen 2 to remove -10 mesh material and provide a fraction containing particles ranging from about 3 1 inch to about 10 mesh. That fraction is sized in screen 3 to provide a first fraction having particles ranging in size from about inch to about inch and a second fraction having particles ranging in size from about A inch to about 10 mesh.

While a first sizing is shown in the attached drawing to i remove -10 mesh, it should be understood that a single sizing operation (e.g., multiple screens) can be employed to simultaneously provide the two desired fractions for gravity separation and the: -10 mesh fraction for processing by wet beneficiation.

' flow middlings,

The 74 inch X V4 inch fraction is removed from screen 3 through line 4 to a gravity separator such as hydrocyclone 5 desirably having a specific gravity of separation of about 2.10 to about 2.16. An underflow containing halite and a substantial portion of the clay initially present in the ore is rejected as tails through line 6 while an overflow containing sylvite values is removed through line 7 and comminuted in crusher 8 to about "V1 inch particles. The comminuted particles are sized on screen 9 to remove -10 mesh material and the A inch X 10 mesh fraction is sent through line 10 to rougher" hydrocyclone 11, having a specific gravity of separation of from about 2.10 to about 2.16. Hydrocyclone 1 1 desirablyprocesses bothV4 inch X 10 mesh particles from crusher 9 and'the V4 inch X 10 mesh particles from screen 3. An underflow containing halite, clay, and the like, is removed as tails through line 12 and an overflow concentrate containing sylvite values is removed from hydrocyclone 11 through line 13.

The overflow concentrate from hydrocyclone 11 is transmitted through line 13 to cleaner hydrocyclone 14 having a specific gravity of separation of from about 2.02 to about 2.06. An overflow sylvite product is removed from hydrocyclone 14 through line 15. Underremoved from hydrocyclone 14 through line 16, are comminuted in crusher 17 to some maximum size between V4 inch and 10 mesh and recycled to screen 2 through line 18. The -10 mesh fractions from screen 2 and screen 9 are deslimed in hydroseparator l9 (desliming may be accomplished separately if desired) and subjected to cationic froth flotation in flotationcircuit 20. Flotation yields a sylvite product which is removed through line 21 and an underflow halite tailings removed through line 22.

It should be noted that the ancillary equipment normally associated with a hydrocyclone is not shown in the attached figure. Thus, for example, if the initial comminution and sizing are dry, fractions will be sent to a pulper wherein the ore is pulped with brine to provide a slurry. if desired, magnetite can also be added to the pulper to provide the requisite media density. It is also possible, however, to employ an initial pulping operation wherein the ore is pulped with brine and subjected to a sizing to remove any -10 mesh particles generated during pulping. The sized material will then be subjected to a second pulping operation in which magnetite and additional brine, if necessary, are added to provide the requisite specific gravity. Similarly, weighting agents or heavy liquids are commonly removed from the hydrocyclone overflow and underflow streams by screening, brine washing, or the like. In the event an intermediate stream containing heavy media or heavy liquids will be processed by further gravity separation, it may be possible to process the stream without intermediate removal of the heavy media or liquid. in such event, care must be taken not to upset the desired gravity in subsequent gravity separation due to uncontrolled carry-over of heavy media or liquid from an earlier gravity separation.

The following Example is included for illustrative purposes only and is not intended to limit the scope of the invention.

AM LE.1---

inch. The ore is sized with a V4 inch screen to provide a inch X V4 inch fraction and a V4 inch fraction. This sizing is referred to hereinafter as the first screening operation. a

The V4 inch X V4 inch fraction from the first sizing operation consists of 270 parts of ore containing 35 parts K 0 and 27 parts clay and is subjected to gravity separation in a first rougher hydrocyclone in which the specific gravity of separation is 2.14. The underflow tails from the separation is 1 60 parts which contains 3 parts K 0 and 23 parts clay (over 38 percent of the clay initially present in the ore). The gravity separation provides parts of overflow containing 32 parts K 0 and 4. parts clay. This fraction is comminuted in a crusher to V4 inch and thereafter is screened to remove -l0 mesh material. This screening, referred to hereinafter as the second screening operation, provides 27 parts of l0 mesh material containing 8 parts K 0 and 1 part clay. The oversize (V4 inch X 10 mesh) from the second screening measures 83 parts and'contains 24 parts K 0 and 3 parts clay.

The undersize from the first screening operation (-V4 inch) consists of 730 parts ore containing 226 parts K 0 and 33 parts clay. It is sized at 10 mesh and provides 350 parts of 10 mesh material containing 109 parts K 0 and 8 parts clay. This sizing is referred to hereinafter astlEihir d screeniiig opei ationfTliebversize from this third screening (V4 inch X 10 mesh) consists of 380 parts material containing 1 16 parts K 0 and 25 parts clay.

The V4 inch X 10'mesh fractions from the second and third screening operations are subjected to gravity separation in a second rougher hydrocyclone having a specific gravity of separation of 2.14. This separation provides 172 parts of underflow tails containing 9 parts K 0 and 24 parts clay. The overflow concentrate consists of 291 parts and contains 131 parts K 0 and 4 parts clay. This concentrate is subjected to a cleaner gravity separation in a hydrocyclone having a specific gravity of separation of 2.04. This gravity separation provides 198 parts of concentrate containing 1 15 parts K 0 and 1 part clay. The underflow from this cleaner gravity separation consists of 93 pa rts containing 16 parts K 0 and 3 parts clay.

The --l0 mesh material from the second and third screening operations and the underflow from the cleaner gravity separation may be subjected to wet beneficiation to recover the values therein. 1

An analysis of the mine run ore and the various fractions is shown in Table 1 below.

The K content noted above, and employed throughout this specification, refers to the potassium values present in the ore as sylvite.

Since variations of the invention will be apparent to those skilled in the art, it is intended that this invention be limited only by the scope of the appendedclaims.

I claim:

1. A process for beneficiating a clay-containing sylvinite ore containing at least about 3 percent clay and having a K O:clay ratio of less than about :1 comprisl. comminuting and sizing said sylvinite ore to provide particles having a maximum size of from about inch to about /2 inch;

2. sizing said comminuted ore of 1 to provide a first fraction containing substantially unliberated particles having sizes greater than about A inch and a second fraction having sizes ranging from about A inch to about mesh;

3; subjecting said first fraction of (2) to gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow fraction characterized by a K ozclay ratio of at least about 8:1 and halite and clay particles are removed as an unde rflow;

4. comminuting said overflow fraction from (3) to i provide about inch substantially liberated particles;

5 sizing said comminuted ore of (4) to provide a third fraction containing particles having sizes ranging from about inch to about 10 mesh and a f t hflaetiqn yi ze mesh; nd...

6 subjecting said second fraction from (2) and third fraction from (5) to gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow concentrate.

6. A process according to claim 1 wherein said third fraction from (5) and said second fraction from (2) are subjected to a rougher gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite and the overflow fromsaid rougher separation is subjected to a cleaner gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite whereby a sylvite-containing overflow concentrate is obtained.

7. A process according to claim 1 wherein l0 mesh particles from step (2) and from step (5) are subjected to wet beneficiation.

8. A process according to claim 7 wherein the wet beneficiation is froth flotation.

9. A process according to claim 7 wherein the combined K Ozclay ratio of said -10 mesh fractions is at least about 8:1.

10. A process according to claim 7 wherein the combined K Ozclay ratio of said l0 mesh fractions is at least about 10:1.

11. A process according to claim 1 wherein the ore is heated to drive off free water before comminution.

12. A process according to claim 6 wherein the underflow from the cleaner gravity separation is subjected to wet beneficiation.

13. A process for beneficiating a clay-containing sylvinite ore containing at least about 3 percent clay and having a K ozclay ratio of less than about 5:1 comprising:

l. comminuting and sizing said sylvinite ore to provide particles having a maximum size of from about /2 inch to about inch; 2. sizing said comminuted ore of l to provide a first ""fraction containing substantially unliberated particles having sizes greater than about 4 mesh and a second fraction having sizes ranging from about 4 mesh to about 10 mesh;

3. subjecting said first fraction of 2) to gravity sepaw' ration in a liquid media having; a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow fraction characterized by a K O:clay ratio of at least about 8:1 and halite and clay particles are removed as an underflow;

4. comminuting said overflow fraction from (3) to provide about 4 mesh substantially liberated particles;

5. sizing said comminuted ore of (4) to provide a third fraction containing particles having sizes a fourth fraction having sizes of IO mesh; and. 6. subjecting said second fraction from (2) and third fraction from (5) to gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow concentrate.

14. A process according to claim 13 wherein the sylvinite ore is comminuted to provide a maximum size of about inch.

15. A process according to claim 13 wherein said gravity separations are vortex gravity separations.

16. A process according to claim. 15 wherein the sylvinite ore is comminuted to provide a maximum size of about inch.

17. A process according to claim 3wherein a magnetite-containing heavy media is employed in the gravity separations.

ranging fron about 4 mesh to about 1 0 meshand 18. A process according to claim 13 wherein said third fraction from and said second fraction from (2) are subjected to a rougher gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite and the overflow from said rougher separation is subjected to a cleaner gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite whereby a sylvitecontaining overflow concentrate is obtained.

19. A process according to claim 13 wherein mesh particles from step (2) and from step (5) are subjected to wet beneficiation.

20. A process according to claim 19 wherein the wet 24. A process according to claim 18 wherein the underflow from the cleaner gravity separation is subjected to wet beneficiation.

232g v UNITED STATES PATENT OFFICE CERTIFICATE. OF CQRRECTION Patent No. 3 ,802, 632 Dated Apr. 9, 1974 Inuentor(s) William B. Dancy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 51 "plug 1/4 plus" should read -p1us l/4-.

Signed and sealed ti'i-iis 15th day of April 1975.

(SLAL) Attest: v H

C I-LKRSRALL DAnN v RUTH C. 21. .3031 Commissioner of Patents (attesting Officer and Trademarks 

2. sizing said comminuted ore of (1) to provide a first fraction containing substantially unliberated particles having sizes greater than about 1/4 inch and a second fraction having sizes ranging from about 1/4 inch to about 10 mesh;
 2. A process according to claim 1 wherein the sylvinite ore is comminuted to provide a maximum size of about 3/4 inch.
 2. sizing said comminuted ore of (1) to provide a first fraction containing substantially unliberated particles having sizes greater than about 4 mesh and a second fraction having sizes ranging from about 4 mesh to about 10 mesh;
 3. A process according to claim 1 wherein said gravity separations are vortex gravity separations.
 3. subjecting said first fraction of (2) to gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow fraction characterized by a K2O:clay ratio of at least about 8: 1 and halite and clay particles are removed as an underflow;
 3. subjecting said first fraction of (2) to gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow fraction characterized by a K2O:clay ratio of at least about 8: 1 and halite and clay particles are removed as an underflow;
 4. comminuting said overflow fraction from (3) to provide about - 1/4 inch substantially liberated particles;
 4. A process according to claim 3 wherein the sylvinite ore is comminuted to provide a maximum size of about 3/4 inch.
 4. comminuting said overflow fraction from (3) to provide about -4 mesh substantially liberated particles;
 5. sizing said comminuted ore of (4) to provide a third fraction containing particles having sizes ranging from about - 1/4 inch to about 10 mesh and a fourth fraction having sizes of -10 mesh; and
 5. sizing said comminuted ore of (4) to provide a third fraction containing particles having sizes ranging from about 4 mesh to about 10 mesh and a fourth fraction having sizes of -10 mesh; and
 5. A process according to claim 3 wherein a magnetite-containing heavy media is employed in the gravity separations.
 6. subjecting said second fraction from (2) and third fraction from (5) to gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow concentrate.
 6. A process according to claim 1 wherein said third fraction from (5) and said second fraction from (2) are subjected to a rougher gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite and the overflow from said rougher separation is subjected to a cleaner gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite whereby a sylvite-containing overflow concentrate is obtained.
 6. subjecting said second fraction from (2) and third fraction from (5) to gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite, whereby sylvite-containing particles are removed as an overflow concentrate.
 7. A process according to claim 1 wherein -10 mesh particles from step (2) and from step (5) are subjected to wet beneficiation.
 8. A process according to claim 7 wherein the wet beneficiation is froth flotation.
 9. A process according to claim 7 wherein the combined K2O:clay ratio of said -10 mesh fractions is at least about 8:1.
 10. A process according to claim 7 wherein the combined K2O:clay ratio of said -10 mesh fractions is at least about 10:1.
 11. A process according to claim 1 wherein the ore is heated to drive off free water before comminution.
 12. A process according to claim 6 wherein the underflow from the cleaner gravity separation is subjected to wet beneficiation.
 13. A process for beneficiating a clay-containing sylvinite ore containing at least about 3 percent clay and having a K2O:clay ratio of less than about 5:1 comprising:
 14. A process according to claim 13 wherein the sylvinite ore is comminuted to provide a maximum size of about 3/8 inch.
 15. A process according to claim 13 wherein said gravity separations are vortex gravity separations.
 16. A process according to claim 15 wherein the sylvinite ore is comminuted to Provide a maximum size of about 3/8 inch.
 17. A process according to claim 3 wherein a magnetite-containing heavy media is employed in the gravity separations.
 18. A process according to claim 13 wherein said third fraction from (5) and said second fraction from (2) are subjected to a rougher gravity separation in a liquid media having a specific gravity of separation intermediate the specific gravities of sylvite and halite and the overflow from said rougher separation is subjected to a cleaner gravity separation in a media having a specific gravity of separation intermediate the specific gravities of sylvite and halite whereby a sylvite-containing overflow concentrate is obtained.
 19. A process according to claim 13 wherein -10 mesh particles from step (2) and from step (5) are subjected to wet beneficiation.
 20. A process according to claim 19 wherein the wet beneficiation is froth flotation.
 21. A process according to claim 19 wherein the combined K2O: clay ratio of said -10 mesh fractions is at least about 8:1.
 22. A process according to claim 19 wherein the combined K2O: clay ratio of said -10 mesh fractions is at least about 10:1.
 23. A process according to claim 13 wherein the ore is heated to drive off free water before comminution.
 24. A process according to claim 18 wherein the underflow from the cleaner gravity separation is subjected to wet beneficiation. 